We determined the effect of three concentrations of gibberellic acid on germination and photoblastic behavior of five species of Opuntioideae from the Mapimi Biosphere Reserve, southern Chihuahuan Desert, Durango, Mexico. For Cylindropuntia imbricata, addition of high concentrations (1,500 ppm) of gibberellic acid gave a 30% germination similar to the control; for Opuntia rastrera, medium concentrations (1,000 ppm) gave <40% germination; and for O. microdasys, low concentrations (500 ppm) gave 35% germination. High concentrations restricted germination. Opuntia macrocentra and Cylindropuntia leptocaulis did not differ significantly from the control. Opuntia macrocentra required light for germination; addition of gibberellic acid did not substitute for light. For all species, light increased germination and the effect of gibberellic acid is species dependent, rarely better than the control. Species we studied did not seem to have physical dormancy and may have had physiological dormancy that was unaffected by gibberellic acid.